Isn't that a lousy move? Doesn't it make the entire theory a tautology that cannot be attacked?

if it's tautological then there's no reason to attack it. It's merely uninteresting. If people still think they don't like it than the critique would have to something else.

Gödel showed that everything is tautological if you go low enough, but invoking it against yourself feels like an automatic point for the other side.

I am not invoking it, of course it is uninteresting. In a sport amongst friends with good intent it should be a suggestion to stay within bounds and satisfy the spirit of the game.

Epoché